It is the latest move by US lawmakers who are determined to keep up the pressure on Great Ormond Street doctors in the on-going international political row over the 11-month-old’s medical care. But legal sources said Charlie is the subject of a High Court order and it made no difference what passport he held. And last Friday, the judge made it clear it would be illegal for Charlie to travel to America without his permission.

The parents’ barrister Grant Armstrong said the parents were of the view that legally it was up to the hospital to change its mind and allow Charlie to be transferred.

But Mr Justice Francis said the effect of the various rulings meant the court’s permission was required.

Great Ormond Street (GOSH) took Charlie’s case to the High Court and a judge agreed to allow them to end Charlie’s treatment because it was not in his ‘best interests’ after he agreed it will cause him pain and will not improve his condition.

The Court of Appeal, the Supreme Court and the European Court of Human Rights all rejected appeals by his parents Chris Gard and Connie Yates, who believe they should have the final say on their son’s treatment.

In Britain the rights of the patient override the wishes of the parents if doctors disagree. For example there are several cases where Jehovah’s Witnesses are given a blood transfusion by doctors despite religious objections from parents.

Can the doctors change their mind and not turn off his life support?

Yes. Great Ormond Street could go back to the High Court to stop the order they fought for this year.

The process of gaining a Consent Order could be done on an urgent basis and completed in less than two hours.

Experts have told MailOnline this is the only way Charlie could travel to America or Rome for treatment because his parents’ appeals appear to have been exhausted.

Can the hospital stop his parents taking him to America without permission?

Yes. If doctors believe that any parent will cause suffering to their child, police can be called in to arrest them using Powers of Protection legislation.

Why won’t the hospital let Charlie die at home?

Connie Yates and Chris Gard say doctors have denied their ‘final wish’ to take Charlie home to die. Travelling to a hospice was also denied. While judges ruled that his treatment should end, there is nothing in the judgments that says the little boy cannot be outside the hospital. Great Ormond Street refused to tell MailOnline on what basis that decision was taken.

If parents still refuse to accept treatment should be withdrawn, can the hospital end it anyway?

Yes. Police could be called in to facilitate treatment being ended if parents were violently preventing it – although it is highly unlikely this would happen. Doctors are more likely to try to ‘persuade’ parents to let it happen.

If the parties remain at loggerheads for a long period the hospital could go back to court for an injunction and ask a judge to set a deadline for treatment to be withdrawn.

A less stringent deadline for Charlie’s life support machine to be shut off was at Midnight last Wednesday, but this has lapsed to allow his parents and loved-ones to say goodbye.

He said: ‘It would be entirely wrong for him to be transferred without my being involved.’

He added that if the hospital did change its mind to allow the baby to go, he would be ‘bound to agree’.

MailOnline previously reported how the hospital could prevent Charlie’s parents from taking him to the US.

If doctors believe that a parent will cause suffering to their child, police can be called in to arrest them using Powers of Protection legislation.

In the case of young cancer sufferer Ashya King his parents faced a European Arrest Warrant after absconding with their son who was in hospital.

Charlie’s parents recently released a new photograph of their little boy where he appears to be looking at a toy to debunk his doctors’ claims he is blind.

Connie Yates and Chris Gard say the poignant image, taken last Friday, is proof that Great Ormond Street Hospital is wrong to write off their 11-month-old son.

His doctors say he is blind, deaf, unable to move and badly brain-damaged and believe it is ‘cruel’ to let him live any longer.

The Mail can reveal that his British clinicians emerged from a crucial summit about his fate yesterday still convinced he should be allowed to die.

They apparently failed to be persuaded by American neuroscientist Dr Michio Hirano, who flew back to New York last night.

Dr Hirano and an expert from the Pope’s hospital in Rome spent five and a half hours trying to talk round Charlie’s doctors.

Last night his mother Connie Yates revealed Charlie was set to undergo more tests.

They could decide if he is fit to undergo experimental treatment on his brain condition.

She added: ‘Our gorgeous baby boy is still stable. We are at his bedside and feel satisfied he is not suffering or in any pain.

‘As Charlie’s loving parents, we are doing the right thing for our son in exploring all treatment options.’

Dr Hirano, from the Columbia University Medical Center, is offering to try the experimental therapy.

It has never been tested on any human or animal.

The expert is at the forefront of researching Charlie’s rare form of mitochondrial disease, and told the High Court last week there was a ‘small but significant’ chance of improvement.

But that was before two brain scans that the 11-month-old had on Sunday, his first since April.

He had an MRI scan and an electroencephalogram (EEG) to monitor brain activity for more than 30 minutes.

Neither the results, nor Dr Hirano’s view of them, have been made public, but were central to yesterday’s meeting of experts at Great Ormond Street Hospital (GOSH) in London.

Dr Hirano, the Rome doctor and Miss Yates were all hoping to convince GOSH doctors to let them try the treatment.

Charlie’s parent said an electroencephalogram (EEG) should be carried out for no longer than 30 minutes.

But specialists said a scan would have to be carried out for at least four hours in order to generate useful data.

Mr Justice Francis has ruled in favour of Ormond Street doctors. He said the scan should ‘be of such duration’ as treating clinicians ‘may advise’.

How does ‘legal permanent residence’ differ from ‘citizenship’?

Becoming a legal permanent resident is also known as getting your green card.

You are not a US citizen but you have the right to live and work in the US permanently.

In addition permanent resident status would guarantee a quick clearance through passport control and immigration, without the need for any formalities

The dispute about the scan arose at the weekend, prior to the expert gathering.

Today Mr Justice Francis released the order he made after analysing emailed arguments from rival legal teams on Saturday.

The order gives an outline of the dispute and his decision.

But they faced a GOSH team including Charlie’s consultant paediatric intensivist, consultant paediatric neurologist, and an expert in mitochondrial disease.

A GOSH spokesman said its position had not changed since last week, when it said Charlie had ‘no quality of life and no real prospect of any quality of life’.

Last night Miss Yates said she and Charlie’s father Chris Gard were ‘so grateful to Dr Hirano and the other clinicians for coming to see Charlie’.

She added: ‘Charlie will be having some more tests shortly.’

Miss Yates was allowed to attend the summit after convincing the High Court judge she should be there. It started at 7.30am and lasted until 1pm.

Mr Justice Francis is due to read a transcript of the meeting before the next hearing, likely to be this Friday.

Charlie’s parents have waged a four-month legal battle to prevent GOSH removing his ventilator. His condition means his lungs are too weak to function by themselves.

His parents say his condition is not this bad and provided the Daily Mail with a photo of him with his eyes open taken last Friday.

The High Court has said it would be kindest to let him ‘slip away’. The Court of Appeal, Supreme Court and European Court of Human Rights agreed.

Charlie has survived three decisions to withdraw his ventilator, but was saved each time by appeals by his parents and interventions from Pope Francis and Donald Trump. Then Dr Hirano and six fellow experts wrote to GOSH offering ‘new evidence’, and the High Court reconvened.